Now I have no idea why someone would have the unauthenticated JSON RPC of their miner exposed to the internet, but then again, these attacks are targeting people who are into cryptocoin mining, so everything is possible.

The command above is then followed by a reboot request:

{"id":0,"jsonrpc":"2.0","method":"miner_reboot"}

The scan is consistent with a vulnerability, CVE 2018-1000049, released in February [2]. The JSON RPC remote management API does provide a function to upload "reboot.bat", a script that can then be executed remotely. The attacker can upload and execute an arbitrary command using this feature. The port the API is listening on is specified when starting the miner, but it defaults to 3333. The feature allows for a "read-only" mode by specifying a negative port, which disables the most dangerous features. There doesn't appear to be an option to require authentication.